There are many occupations such as shipbuilding, mining, plumbing, carpet and floor installation, construction, repair, services, and auto body repair in which people must spend a considerable amount of time kneeling or squatting. Such people put 70% of their body weight on a few cubic centimeters of the tibia and patella while kneeling as opposed to putting 22% of their body weight on each knee while walking. Prolonged kneeling increases a person's risk of developing musculoskeletal knee disorders such as osteoarthrosis, meniscal lesions, chondromalacia, and bursitis. Also, it is uncomfortable to maintain a kneeling position for a long period, which can decrease productivity of workers.
Various studies have been made on injury to the knee from prolonged kneeling or squatting. Elsner et al., [Knee Joint Arthroses and Work-Related Factors] Soz Praventivmed, 1996; 41(2):98–106, found that men who worked on their knees had a significantly greater chance of developing arthrosis of the knee. Cooper et al., Occupational Activity and Osteoarthritis of the Knee, Ann Rheum Dis 1994 February; 53(2):90–3, found that men whose job entailed more than 30 minutes per day of squatting or kneeling had a significantly greater chance of developing osteoarthritis.
Kivimaki et al., Knee Disorders in Carpet and Floor Layers' and Painters, Scand J Work Environ Health 1992 October; 18(5):310–6, and Occupationally Related Ultrasonic Findings in Carpet and Floor Layers' Knees, Scand J Work Eviron Health 1992 December; 18(6):220–2, found that osteophytes of the patella were more common among carpet and floor layers than among painters, and that self-reported knee bursitis was also more prevalent in carpet and floor layers. Furthermore, ultrasonography of the knee showed thickening of the prepatellar or superficial infrapatellar bursa in 49% of the carpet and floor layers and 7% of the house painters. This ultrasonographic finding was associated with knee pain in kneeling postures.
Thun et al., Morbidity from Repetitive Knee Trauma in Carpet and Floor Layers, Br J Ind Med 1987 September; 44(9):611–20, found that self reported bursitis and arthritis of the knee were more common in terazzo workers who kneel than in other groups who seldom kneel. Coggon et al., Occupational Physical Activities and Osteoarthritis of the Knee, Arthritis Rheum 2000 July; 43(7):1443–9, found that the risk of developing knee osteoarthritis is higher for people who kneel or squat for prolonged periods of time. Sandmark et al., Primary Osteoarthrosis of the Knee in Men and Women as a Result of Lifelong Physical Load from Work, Scand J Work Environ Health 2000 February; 26(1):20–5, found that among men there is an association between kneeling and knee osteoarthrosis.
Kasch and Enderlein, [Damage to the Knee Joint in Ship Building] Beitr Orthop Traumatol 1986 October; 33(10):487–94, reported that x-rays showed that there was an increased occurrence of knee injuries in welders as compared to other groups.
A study of ergonomics and shipbuilding by the National Institute for Occupational Safety and Health (NIOSH) found that kneeling or squatting for long periods of time may be related to the finding that the incidence of lower extremity musculoskeletal injury in domestic shipbuilding and ship repair industries is 300–220 percent higher than in the overall manufacturing sector. NIOSH also found that knee injuries have the highest cost compared to other injuries per employee per year.
The health risks and costs associated with prolonged kneeling and squatting have led to efforts to prevent such injuries. Such efforts have recognized the need to reduce the amount of flexion in the knee and the amount of contact stress applied to the facet of the knee joint. Efforts to reduce such stress would also reduce forces on the internal knee and lower back that are known risk factors for musculoskeletal knee disorders. Unfortunately, many of the devices that have been used in the past to relieve pressure on the knees are bulky, heavy, and of questionable durability.
U.S. Pat. No. 3,025,526 discloses a kneeling device that attaches to a user's leg. It includes a kneepad that is attached to the user's knee by straps that are positioned below the knee and in the ankle region. When a user is in the standing position, the device unfolds and rests partially on the thigh. This device is bulky and restricts a user's movements while walking. Also, it is essentially a kneepad and does not take the weight off the user's knee.
U.S. Pat. No. 4,772,071 discloses a kneeling device that inlcudes a kneepad attached to a seat. The device is attached to the lower leg. The device is, however, bulky and must be removed when the user wants to stand or walk because it hampers movement.
In U.S. Pat. No. 5,865,507, a rectangular base has a seat and a pair of coextensive troughs with knee-wells located at the ends of the troughs. A user sits in the seat and places his legs in the troughs and his knees in the knee-wells. The device is also bulky and can only be used on unobstructed horizontal surfaces. Furthermore, it is not easily moveable, and every time a user wants to change his position, he must stand up and lift the device to move it. The device is heavy and can cause tripping because of its bulkiness.
U.S. Pat. No. 6,089,667 describes a motorized knee support device comprising a rigid plate that is covered with a pad. The plate is mounted on a base by a threaded post, and the height of the plate can be adjusted by a gear system. The device is relatively difficult to mount because it requires a person to stand in front of the unit, squat or kneel down, and then extend the leg back underneath the support. It is also not portable, but rather is freestanding, heavy, and bulky.
U.S. Pat. No. 5,577,800 discloses a work seat that is used while in a kneeling position. The device has a base with wheels, an adjustable seat, and a handle. The device allows the user, while kneeling, to support body weight primarily on the device rather than on the knees. The device, however, is bulky, heavy, and can only be used on unobstructed surfaces, thus there are many places where it cannot be used. Also, the wheels only move forward and backward. Thus the user must dismount when the device needs to be moved laterally.
In U.S. Pat. No. 5,380,021, a mobile knee support includes a pair of slings supported by a pair of casters. The slings support the knees of the user, and the casters allow for mobility. Since the user's weight is distributed on the knees, the device does not reduce forces on the internal knee and lower back. Also, the device does not reduce flexion in the knee joint. Since there are wheels, it can only be used on a relatively level, smooth, and unobstructed surface.
A sit-kneel chair is shown in U.S. Pat. No. 4,589,699. The chair has a seat portion and a knee support which are designed primarily to relieve tension of the lower back. Since the user sits in an upright position, the device is not suitable for use when kneeling close to the ground.
U.S. Pat. No. 4,377,309 discloses another support device having a seat attached to a base, for supporting the user in a sitting-kneeling position.
Balans Produkter AB produces a device under the trademark Balans Snap Sit, which includes a knee-well attached to a seat. The device does not fold while attached to the leg, and it is bulky and restricts movement while walking. It is also flammable, not sufficiently durable for regular use by workers in heavy industry, and has knee-wells that can gather materials, such as weld slag.
There is thus a need for a device that relieves pressure from the knees while kneeling, is easily portable, is attachable to the body, and can be moved automatically by the user without the user having to pick up the device and manually move it to a new position. There is also independently a need for a device that that is nonflammable and durable, so that it can be used in heavy industry and can be used on horizontally constrained and uneven surfaces. It would also be helpful to provide such a device that is comfortable to use while kneeling.